1. Field of the Invention
The invention is directed to control of a printer carriage in an ink jet printer which prints by reciprocal scans of a print head. In particular, the present invention relates to control of such a printer so as to accommodate speed non-uniformities and image degradation that result from high speed movement of an ink jet head.
2. Description of the Related Art
Ink jet printers have become increasingly popular for printing text, continuous data such as non-color graphics, and color images from a host computer onto recording media. In addition, ink jet print heads increasingly are used in devices other than printers, such as copying machines. The demand for faster ink jet printing techniques has grown along with this increased prevalence of ink jet printing.
One technique for increasing the speed of ink jet printing is to increase the speed at which an ink jet print head scans across a recording medium, for example by using a faster motor to drive an ink cartridge receptacle that holds an ink jet cartridge having the print head. However, faster motors tend to suffer from greater speed non-uniformities than slower motors, particularly at the start of a scan operation. These speed non-uniformities can result in rippled or otherwise degraded image formation.
Another technique for increasing the speed of ink jet printing is to use bi-directional printing, in which ink is ejected from a print head during both forward and reverse scans across a recording medium. However, in bi-directional printing, speed non-uniformity occurs on opposite sides of a recording medium from scan line to scan line. As a result, distortions caused by speed non-uniformity at a start of each scan line become more noticeable by proximity to vertically-adjacent non-distorted ends of previous and subsequent scan lines.
In addition, high-speed bi-directional printing can exacerbate a satelliting effect that can occur when ink is ejected from a print head. When a main droplet of ink is ejected from an ink jet print head so as to record a pixel, a small satellite droplet often is also ejected. Ink jet print heads typically are angled slightly with respect to a recording medium so that the satellite droplet overlaps the main droplet when the print head is scanned across a recording medium in a forward direction. However, in the reverse direction, this angling tends to cause the satellite droplet to land near an edge of or even outside of the main droplet, resulting in a small satellite being recorded next to each recorded pixel during a reverse scan.
Furthermore, as carriage scanning speed increases, the satellite droplet tends to travel farther from the main droplet before striking the recording medium, resulting in satellites appearing farther from each pixel. As a result, the satellites tend to become more noticeable, particularly in the case that continuous images are recorded. Thus, increased scanning speed tends to increase image degradation caused by the satelliting effect.
Accordingly, what is needed is a way to address image degradation and satelliting effects that result when using faster carriage motors in an ink jet printer that can exhibit increased speed non-uniformity.
The invention addresses motor speed non-uniformity at a start of a scan line by printing with a lateral scan process that does not use a critical zone for printing at edges in a lateral scan of the print head. This critical zone is a zone in which printing of continuous images (e.g., non-color graphics such as tables or charts) with speed non-uniformity can result in noticeable ripple effects and image degradation.
In one embodiment, the lateral scan process inserts a margin into a scan line so as to allow a print head to traverse the critical zone before ejection of ink begins. As a result, speed non-uniformities tend to dissipate to less noticeable levels before printing a scan line. The margin preferably is not added to scan lines for isolated (e.g., text) scan lines, because ripple effects from speed non-uniformity are less noticeable in text. Thus, a balance is achieved between image quality and a time needed for a print head to traverse scan lines.
Accordingly, in one aspect the invention is a method for printing on a recording medium by lateral scans of a print head in accordance with print data. In this aspect, a content of print data is determined. Then, the print data is printed either with a first lateral scan process using a critical zone at edges in a lateral scan of the print head for printing, or with a second lateral scan process that does not use the critical zone for printing. The first or second lateral scan process is selected based on the print data.
The critical zone is an unstable zone for moving the print head in a lateral scan. Preferably, the critical zone is sized in correspondence with ramp up non-uniformities of a print carriage on which the print head is mounted, so as to accommodate a distance between a point where print degradation due to speed non-uniformities are noticeable to a point where print degradation due to speed non-uniformities are no longer noticeable.
The second lateral scan process preferably is a process in which a predetermined margin is inserted into the first lateral scan process. The second lateral scan process is used if print data for a current scan and print data for a previous scan, in at least the critical zone, are continuous print data, thereby alleviating ripple effects for the continuous data. In a case where the print data for the current scan and the print data for the previous scan are not continuous print data, the print data preferably is printed using the first lateral scan process.
By virtue of the foregoing, ripple of continuous images due to speed non-uniformity is alleviated through use of an inserted margin, while faster printing speed is maintained for non-continuous data.
Preferably, it is determined whether or not print data for a current scan and print data for a previous scan, in at least the critical zone, are continuous print data. The current scan is printed in a direction opposite to that of the previous scan by the first lateral scan process in a case that the print data for the current scan and the print data for the previous scan are not continuous print data. The current scan is printed in a same direction as that of the previous scan by the second lateral scan process in a case that the print data for the current scan and the print data for the previous scan are continuous print data.
By virtue of the foregoing, bi-directional printing that includes printing in the critical zone is used for isolated (e.g., text) scan lines, where distortion from speed non-uniformity is less noticeable, thereby improving printing speed. Unidirectional printing that does not include printing in the critical zone is used for scan lines of continuous images, thereby alleviating image distortion from speed non-uniformity where such distortion is most noticeable.
In another aspect, the invention concerns a method for forward and reverse printing on a recording medium by reciprocal forward and reverse scans of a print head in accordance with print data. According to this aspect, print data is printed in one direction of the reciprocal forward and reverse scans of the print head, and print data is printed in another direction of the reciprocal forward and reverse scans so that the printed data in the other direction is laterally shifted a predetermined distance as compared to printing where each pixel printed in the other direction vertically matches each pixel printed in the one direction. Preferably, the predetermined distance is a distance corresponding to one fourth of a printed pixel. This lateral shift tends to mask satelliting effects, particularly in the case of printing continuous image data.
In yet other aspects, the invention concerns a printer driver and an apparatus that utilize the foregoing methods for reducing image degradation.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiment thereof in connection with the attached drawings.
FIG. 1 shows a perspective view of computing equipment used in connection with the printer of the present invention.
FIG. 2 is a front perspective view of the printer shown in FIG. 1.
FIG. 3 is a back perspective view of the printer shown in FIG. 1.
FIG. 4 is a back, cut-away perspective view of the printer shown in FIG. 1.
FIG. 5 is a front, cut-away perspective view of the printer shown in FIG. 1.
FIG. 5A is a top-down plan view of the printer shown in FIG. 1.
FIG. 5B shows a face-on view of clutch plate and gears operated by both line feed motor and carriage motor of the printer shown in FIG. 1.
FIG. 5C is a flow diagram which depicts operation of the automatic sheet feeder process for the printer of the present invention.
FIG. 5D is a flow diagram which depicts operation of the capping and purge process for the printer of the present invention.
FIG. 6 shows an example of a disposable ink cartridge used with the present invention.
FIG. 7 shows a face-on view of head configurations for print heads used with the present invention.
FIG. 8 is a block diagram showing the hardware configuration of a host processor interfaced to the printer of the present invention.
FIG. 9 shows a functional block diagram of the host processor and printer shown in FIG. 8.
FIG. 10 is a block diagram showing the internal configuration of the gate array shown in FIG. 8.
FIG. 11 shows the memory architecture of the printer of the present invention.
FIG. 12 shows an overall system flowchart detailing the operation of the printer of the present invention.
FIG. 13 is a flowchart showing print control flow in accordance with the present invention.
FIG. 14 depicts a table showing command flow during a printing sequence.
FIG. 15 is a flow diagram which depicts a hard power-on sequence for the printer of the present invention.
FIG. 16 is a flow diagram which depicts a soft power-on sequence for the printer of the present invention.
FIG. 17 is a flow diagram which depicts a soft power-off sequence for the printer of the present invention.
FIG. 18 illustrates communication according to the preferred embodiment of the invention between an application program and other operations running on a host processor and various tasks running on a printer according to the preferred embodiment of the invention.
FIG. 19 is a flow diagram illustrating controller timer control according to a cyclic handler for controlling timer operations.
FIG. 20 is a flow diagram which depicts printer driver software process flow.
FIG. 21A is a flow diagram which depicts automatic sheet feed sequence of the present invention.
FIG. 21B is a continuation of the automatic sheet feed sequence shown in the automatic sheet feed sequence of FIG. 21A.
FIG. 21C is a flow diagram which depicts the early success logic shown in the automatic sheet feed sequence of FIG. 21A.
FIG. 21D is a flow diagram which depicts the load speed select for the automatic sheet feed sequence shown in FIG. 21A.
FIG. 21E is a flow diagram which depicts the recovery sequence as shown in the automatic sheet feed sequence of FIG. 21A.
FIG. 22 is a flow diagram which depicts an automatic sheet feed sequence for a first page within a printer.
FIG. 23 is a flow diagram which depicts an automatic sheet feed sequence after an eject sequence in a printer.
FIG. 24 is a flow diagram which depicts printer driver logic for the selection of line feed, paper load and eject speeds.
FIG. 25 is a flow diagram which depicts eject speed override logic of the present invention.
FIG. 26 is a flow diagram which depicts line feed speed override logic of the present invention.
FIG. 27A is a representative view of for describing carriage control for printing text, continuous images, and color images.
FIG. 27B is a representative view for describing carriage direction control for scan lines which include both non-color continuous and color images.
FIGS. 27C to 27G are tables for determining print direction and other print information based on print mode, head type, paper type, and print data type.
FIG. 28 is a representative view for explaining movement of print heads according to the invention.
FIG. 29 is a flowchart for describing a SKIP command issued by a printer driver according to the invention.
FIG. 30 is a flowchart for describing a PRINT command issued by a printer driver according to the invention.
FIG. 31 is a flowchart for describing a DIRECTION command issued by a printer driver according to the invention.
FIG. 32 is a flowchart for describing an EDGE command issued by a printer driver according to the invention.
FIG. 33 is a flowchart for describing determination of a scan margin by a printer driver according to the invention.
FIG. 34 is a flowchart for describing a NEXT_MARGIN command issued by a printer driver according to the invention.
FIG. 35 is a flowchart for describing an AT_DELAY (automatic delay) command issued by a printer driver according to the invention.
FIG. 36 is a flowchart for describing a carriage task performed by a printer control according to the invention.
FIG. 37 is a flowchart for describing a first carriage scan control called by the carriage task of FIG. 36.
FIG. 38 is a flowchart for describing a second carriage scan control called by the carriage task of FIG. 36.
FIGS. 39a and 39b are representative views for describing satellite control according to the invention.
FIG. 40 is a flowchart for describing carriage motor start performed by a printer control according to the invention.
FIG. 41 is a flowchart for describing a carriage interrupt process performed by a printer control according to the invention.
FIG. 42 is a flowchart for describing automatic trigger delay performed by a printer control so as to alleviate satelliting according to the invention.
FIG. 43 is a flow diagram which depicts a printer driver software alignment process of the present invention.
FIG. 44 is a series of print mode tables for printing with alignment and without alignment pursuant to the printer driver software alignment process of FIG. 43.
FIG. 45 is a flow diagram of processor-executable process steps to print color data.
FIG. 46 illustrates printing of color data and black data using two different ink jet print heads.
FIG. 47 is a diagram for describing prefire control in which a prefiring operation is performed at a predetermined interval.
FIGS. 48 and 49A to 49C are diagrams for describing image degradation that can result from inadequate prefiring.
FIG. 50 is a diagram for describing prefire control according to the invention.
FIG. 51 is a flowchart for describing prefire control timing according to the invention.
FIG. 52 is a flowchart for describing an update of prefire timers by a printer controller according to the invention.
FIG. 53 is a flowchart for describing a prefire check operation performed by a printer controller according to the invention.
FIG. 54 is a flowchart for describing generation of a nozzle-number-change prefire request by a printer driver according to the invention.
FIG. 55 is a flowchart for describing scan prefire processing by a printer controller according to the invention.
FIG. 56 is a flowchart for describing a prefire (print) function according to the invention.
FIG. 57 is a diagram for describing a relationship between ink jet nozzle heat pulse width and output images.
FIG. 58 is a diagram for describing a heat pulse width modulation.
FIG. 59 is a flowchart for explaining control of nozzle heat pulse driving times.
FIG. 60 is a diagram showing exploded views of tables for heat-up coefficients and tables for driving times stored in a printer.
FIG. 61 is a flowchart for describing use of a real-time environmental temperature for determination of driving times.
FIG. 62 is a diagram for describing heat pulse width modulation during printing of plural scan lines.
FIG. 63 is a diagram for describing heat pulse width modulation according to the invention in which a heat pulse width is maximized after a first time interval since a previous prefire operation.
FIG. 64 is a flowchart for describing heat pulse width modulation according to the invention in which a heat pulse width is maximized after a first time interval since a previous prefire operation.
FIG. 65 is a flow diagram of computer-executable process steps to produce binarized data for five different inks based on RGB data of a pixel.
FIG. 66 illustrates a graph of input values versus output values for performing output correction on input values corresponding to five different types of ink.
FIG. 67 is a functional block diagram showing computing equipment communicating with the printer.
FIG. 68 is a flow diagram illustrating how print driver obtains status from printer and modifies processing of print data generation.
FIG. 69 illustrates a flow sequence executed by print controller.
FIG. 70 illustrates process steps for bleed reduction.
FIG. 71 is a graph of color values.
FIG. 72 illustrates values stored in Color Table 1 as opposed to values stored in Color Table 2.
FIGS. 73A and 73B are flow diagrams for implementing smear control processing.
FIG. 74 is a flow diagram illustrating how the print driver sets the value for the smear timer.
FIG. 75 is a flow diagram illustrating how the print driver sets the density threshold for smear control.
FIGS. 76 and 77 are flow diagrams for explaining how the print driver modifies speed at which the printer feeds sheets from the feed tray.
FIG. 78 is a flow diagram for explaining how the print driver modifies the operational parameter of the printer that controls the timing for pre-fire operations.
FIG. 79 shows a portion of user interface displayed by the print driver on the display.
FIG. 80 is a flow diagram for explaining how the print driver modifies its own operation based on status of the printer.
FIG. 81 illustrates modification of purge speed in the printer.
FIG. 82 illustrates modification of print driver operations.